The field of art to which this invention pertains is explosive and thermic compositions or charges.
For many years water soluble inorganic oxygen supplying salts, such as nitrates, chlorates and perchlorates, have been used in explosive compositions. Ammonium nitrate and sodium nitrate, in particular, find extensive use in commercial high explosives and blasting agents. Of necessity, such explosives often are stored under conditions of high relative humidity and are used under wet conditions. The hygroscopicity and water solubility of the inorganic oxygen supplying salts are undesirable characteristics which may lead to deterioration of the explosive composition and to failures in use.
Because of this deteriorating action, extensive precautions are taken to exclude water from such compositions, not only during formulation, but also in packaging, storage and use, or to at least minimize the amount of water entering the composition. Hence, these products have been packed in waterproof closed metal containers, in highly water resistant laminated fiberboard containers, in heavily waxed paper cartridges, or in water resistant plastic films.
One of the most widely used explosives is based upon ammonium nitrate and fuel oil which is called ANFO in the industry. Such explosive compositions being based on ammonium nitrate must be kept dry in order to be useful. As pointed out in U.S. Pat. No. 3,153,606, such explosive compositions have been blended with finely divided water-dispersible starches and gums. When first contacted with water, such gums form a paste in the outer part of the explosive which paste retards the rate of water penetration into the interior of the charge and prevents segregation of the original components of the mixture and detonation failures. If exposed to moisture over an extended time period, however, the moisture tends to penetrate into the interior of the explosive composition and, thereby, ruining it or at least decreasing its explosive effectiveness.
The present invention provides waterproof explosive compositions which can tolerate extended exposure to moisture.